title: The role of commitment strength in enhancing safe water consumption: mediation analysis of a cluster-randomized trial.
abstract: OBJECTIVE
  The objectives of this study were to investigate the importance of commitment strength in the theory of planned behaviour (TPB) and to test whether behaviour change techniques (BCTs) aimed at increasing commitment strength indeed promote switching to arsenic-safe wells by changing commitment strength.
  
  
  METHODS
  A cluster-randomized controlled trial with four arms was conducted to compare an information-only intervention to information plus one, two, or three commitment-enhancing BCTs.
  
  
  METHODS
  Randomly selected households (N = 340) of Monoharganj, Bangladesh, in seven geographically separate areas, whose members were drinking arsenic-contaminated water at baseline and had access to arsenic-safe wells, participated in this trial. The areas were randomly allocated to the four intervention arms. Water consumption behaviour, variables of the TPB, commitment strength, and socio-demographic characteristics were assessed at baseline and at 3-month follow-up by structured face-to-face interviews. Mediation analysis was used to investigate the mechanisms of behaviour change.
  
  
  RESULTS
  Changes in commitment strength significantly increased the explanatory power of the TPB to predict well-switching. Commitment-enhancing BCTs - public self-commitment, implementation intentions, and reminders - increased the behaviour change effects of information by up to 50%. Mediation analyses confirmed that the BCTs indeed increased well-switching by increasing commitment strength. Unexpectedly, however, mediation via changes in behavioural intentions was the strongest mechanism of the intervention effects.
  
  
  CONCLUSIONS
  Commitment is an important construct to consider in water- and health-related behaviour change and may be for other health behaviours as well. BCTs that alter behavioural intentions and commitment strength proved highly effective at enhancing the behaviour change effects of information alone. Statement of contribution What is already known on this subject? Millions of people drink contaminated water even if they have access to safe water alternatives and despite increased awareness of the consequences to health. The theory of planned behaviour (TPB) and commitment strength are predictive of safe water consumption. The potentially commitment-enhancing behaviour change techniques (BCTs) - reminders, implementation intentions, and public self-commitment - can promote health behaviours, including safe water consumption. What does this study add? Changes in commitment strength significantly added to the prediction of switching to arsenic-safe wells by the TPB. Information-plus-BCTs aimed at increasing commitment strength led to >50% more well-switching than information alone. Behaviour change effects of the BCTs were mediated by changes in commitment strength and behavioural intentions.
authors.affiliation: Department of Environmental Social Sciences, Eawag: Swiss Federal Institute of Aquatic Science & Technology, Duebendorf, Switzerland; Department of Psychology, University of Konstanz, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Inauen
authors.forename: Robert
authors.initials: R
authors.lastname: Tobias
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Mosler
mesh_terms: D000328:Adult; D020261:Arsenic Poisoning / Q000517:prevention & control; D001294:Attitude to Health; D001459:Bangladesh; D004326:Drinking; D060766:Drinking Water; D005260:Female; D015438:Health Behavior; D006266:Health Education; D006293:Health Promotion / Q000379:methods; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D009042:Motivation; D011582:Psychological Theory
chemical_list: D060766:Drinking Water
keywords: Bangladesh; behaviour change; commitment strength; implementation intentions; prompts; public self-commitment; reminders; safe water consumption; theory-based intervention